In connection with liquid dispensing assemblies, and more particularly, in connection with liquid dispensing assemblies which are being used to dispense hot melt adhesives or other thermoplastic materials, a typical dispensing assembly conventionally comprises a supply source of the adhesive or thermoplastic material, and means for precisely or accurately metering and pumping the adhesive or thermoplastic material toward an applicator head or dispensing assembly. In connection with particular applications or procedures, it is necessary to accurately or precisely meter the liquids being dispensed so as to ensure that a specific or predetermined volume of the liquid is in fact dispensed within a specific or predetermined period of time. For example, in connection with the dispensing of hot melt adhesive materials, it is often necessary to provide a plurality of individual pumps for providing predetermined volumes of the adhesive material, which may in fact comprise similar or different volume quantities or amounts, to discrete, separate, or respective applicator or dispensing outlets. The individual pumps conventionally comprise rotary gear pumps which are operatively connected to a drive motor through means of a common rotary drive shaft, and dynamic seals, that is, stationary seals which are operatively disposed around or operatively associated with the rotary drive shaft, are provided for effectively preventing any external or outward leakage of the hot melt adhesive material from the assembly at the interfaces defined between the rotary drive shaft and the rotatably driven gears of the rotary gear pumps. An example of such a conventional or PRIOR ART hot melt adhesive rotary gear pump assembly is disclosed, for example, within U.S. Pat. No. 6,422,428 which issued to Allen et al. on Jul. 23, 2002.
More particularly, as disclosed within FIG. 1, which corresponds substantially to FIG. 3 of the aforenoted patent to Allen et al., one of a plurality of gear pump assemblies, as utilized within a hot melt adhesive applicator assembly, is disclosed at 20, and it is seen that each gear pump assembly 20 comprises a conventional sandwiched construction comprising three plates 220,222,224 encompassing or enclosing a pair of gears 230,232. Gear 230 comprises an idler gear, whereas gear 232 comprises a driven gear which is operatively mounted upon a rotary drive shaft 234. The rotary drive shaft 234 has a hexagonal cross-sectional configuration so as to effectively define or provide the drive connection with the driven gear 232, and it is noted that the drive shaft 234 extends through each one of the gear pump assemblies 20. A pair of seals 240, only one of which is shown in FIG. 1, are provided within suitable apertures defined within the end plates 220,224 so as to annularly surround the rotary drive shaft 234 and thereby prevent any leakage of the hot melt adhesive material out from the gear pump assembly 20. A threaded port 244 is provided for receiving a temperature sensor for ensuring that each gear pump assembly 20 has been heated to a predetermined temperature level prior to operation, and a rupture disk assembly 242 is provided for pressure relief under overpressure conditions. A bore 248 is provided for receiving a pressure transducer which can read output liquid pressure, and when the pressure transducer is not being utilized, a plug assembly 250 is adapted to be disposed within the bore 248.
While a gear pump assembly 20 such as that disclosed within the aforenoted patent to Allen et al. is operatively viable, the gear pump assembly 20 of the aforenoted type nevertheless exhibits several operative drawbacks and disadvantages. Firstly, for example, it is noted that in view of the fact that the seals 240 of the gear pump assembly 20 are located upon external surface portions of the end plates 220, 224 of the gear pump assembly 20, should the seals 240 experience failure, external leakage of the hot melt adhesive material poses obvious maintenance problems, not to mention the likelihood of the leaking hot melt adhesive material causing fouling of other operative components of the gear pump assembly 20. In addition, it has been noted in the aforenoted patent to Allen et al. that the rotary drive shaft 234 extends through each one of the gear pump assemblies 20. Accordingly, if, for example, one of the gear pump assemblies 20 should experience failure or exhibit leakage, and therefore needs to be removed for repair or replacement, the particular gear pump assembly 20 cannot in fact simply be removed from the overall hot melt adhesive dispensing assembly comprising the plurality of gear pump assemblies 20. To the contrary, and more particularly, the rotary drive shaft 234 must firstly be removed so as to subsequently permit the particular gear pump assembly 20 to be removed and separated from the other gear pump assemblies 20 in order to repair or replace the failed or leaking gear pump assembly 20. Upon completion of the repair or replacement of the failed or leaking gear pump assembly 20, the repaired gear pump assembly 20, or the new gear pump assembly 20, can effectively be re-inserted into the bank or array of gear pump assemblies 20 whereupon, still further, the rotary drive shaft 234 can be re-installed in connection with the plurality of rotary gear pump assemblies 20 so as to again be operatively engaged with each one of the plurality of rotary gear pump assemblies 20. Still yet further, if one of the gear pump assemblies 20 should experience failure and effectively become frozen, the failed and frozen gear pump assembly 20 will effectively prevent rotation of the rotary drive shaft 234 whereby the failed or frozen gear pump assembly 20 can experience or undergo further damage, and in turn, cause opeerative freezing or failure of the other gear pump assemblies 20 which are rotatably engaged with and driven by means of the common rotary drive shaft 234.
Accordingly, a need existed in the art for a new and improved gear pump assembly for use in connection with liquid dispensing assemblies wherein the liquid dispensing assembly would comprise a plurality of rotary, gear-type pump assemblies which are mounted upon the liquid dispensing assembly such that all of the gear pump assemblies would be independent with respect to each other, wherein the plurality of rotary, gear-type pump assemblies would be operatively driven by means of a common rotary drive shaft in such a manner that no external dynamic seals would be required, wherein any particular one of the rotary, gear-type pump assemblies could be readily removed from the array or bank of rotary, gear-type pump assemblies independently of the other rotary, gear-type pump assemblies, and subsequently be re-inserted into the array or bank of rotary, gear-type pump assemblies, or replaced by means of a new rotary, gear-type pump assembly, and wherein still further, as a result of the plurality of rotary, gear-type pump assemblies being independent with respect to each other and not being operatively driven by means of, or mounted upon, a common internally disposed rotary drive shaft, then should a particular one of the rotary, gear-type pump assemblies experience a failure, the failed rotary, gear-type pump assembly would not experience additional damage or cause the other rotary, gear-type pump assemblies to experience freezing or failure. The aforenoted need in the art was addressed by means of the rotary, gear-type pump assemblies disclosed U.S. Pat. No. 6,688,498 which issued to McGuffey on Feb. 10, 2004, which patent is hereby incorporated herein by reference.
More particularly, as disclosed within FIG. 2, which corresponds substantially to FIG. 4 of the aforenoted patent to McGuffey, it is seen that each one of the rotary, gear-type pump assemblies 310 comprises a housing defined by means of a sandwiched construction which includes an intermediate or central plate 316. The central or intermediate plate 316 is provided with a plurality of cutout regions 318, 320,322, and a plurality of gear members 324,326,328 are respectively rotatably disposed within the cutout regions 318, 320,322 such that the three gear members 324,326,328 are disposed in a substantially coplanar manner with respect to the central or intermediate plate 316. Gear member 324 comprises a pump driven gear, gear member 326 comprises a pump drive gear which is operatively enmeshed with the pump driven gear 324, and gear member 328 comprises a pump idler gear which is operatively enmeshed with the pump drive gear 326. Each one of the gear members 324,326,328 is respectively fixedly mounted upon a pin, axle, or shaft member 330, and opposite ends of the gear pins, axles, or shafts 330 are rotatably disposed within bearing members which, while not being shown within FIG. 2, are fully disclosed and illustrated within the aforenoted patent to McGuffey. The bearing members, not shown, are, in turn, disposed within recesses which are defined within or upon interior side surface portions of the side plates of the housing sandwich structure.
In this manner, the gear members 324,326,328 are effectively rotatably mounted internally within the housing sandwich structure. This particular structural arrangement, by means of which the gear members 324,326,328 are mounted upon the side plates of the rotary, gear-type pump assembly 310, is one of the critically important, and unique and novel, features characteristic of the rotary, gear-type pump assembly 310, as constructed in accordance with the principles and teachings of the invention as set forth in the aforenoted patent to McGuffey, and which will likewise play a critically important inventive role in connection with the present invention as will be set forth hereinafter. More particularly, it is noted that all of the rotary shafts 330 and the bearing members, not shown, are disposed in an entirely enclosed or encased manner within the internal confines of the sandwiched plate construction comprising the housing of the rotary, gear-type pump assembly 310. Viewed from a different point of view, none of the rotary shafts 330 and bearing members, not shown, project outwardly through, or extend externally of, the side plates of the gear pump housing, and in this manner, the need for external dynamic shaft seals, which have often conventionally proven to be sources of external leakage of the fluid being pumped and dispensed by means of the rotary, gear-type pump assembly 310, has effectively been eliminated or obviated. It is noted further that in order to fixedly secure together the plate members comprising the sandwiched construction of the housing of the rotary, gear-type pump assembly 310, as well as to ensure the proper coaxial alignment of the bearing member recesses defined within the side plates of the gear pump housing, with respect to the cutout regions 318,320,322, defined within the central or intermediate plate 316, so as to properly house, accommodate, and mount the three gear members 324,326,328, and their associated shafts 330 and bearing members, not shown, upon the plate members of the rotary, gear-type pump assembly 310, a plurality of screws and alignment pins extend through suitable bores, not numbered for clarity purposes, which are defined within the plate members of the rotary, gear-type pump assembly 310 as can be seen in connection with central or intermediate plate 316.
With reference continuing to be made to FIG. 2, and as will be more fully appreciated hereinafter, each one of the pump driven gears 324 of each one of the rotary, gear-type pump assemblies 310 is adapted to be drivingly enmeshed with a manifold pump drive gear, not shown within FIG. 2 but fully disclosed and illustrated within the aforenoted patent to McGuffey, wherein the plurality of manifold pump drive gears are drivingly or rotatably mounted upon a common drive shaft which extends axially through a drive gear manifold, also not shown within FIG. 2 but fully disclosed and illustrated within the aforenoted patent to McGuffey. The drive shaft, for rotatably driving all of the manifold pump drive gears, is adapted to be driven by means of a suitable drive motor and gearbox assembly, also not shown within FIG. 2 but fully disclosed and illustrated within the aforenoted patent to McGuffey, and the hot melt adhesive material, to be metered and dispensed by means of each one of the rotary, gear-type pump assemblies 310, is introduced into the drive gear manifold by means of a liquid inlet support port to which a suitable supply hose is connected so as to conduct hot melt adhesive material thereinto from an external or remote adhesive supply unit (ASU).
When the hot melt adhesive material is introduced into the drive gear manifold, the hot melt adhesive material will enter liquid supply cavities which are respectively defined around each one of the manifold pump drive gears, and each one of the liquid supply cavities is, in turn, respectively fluidically connected to a liquid accumulator cavity which is located at the enmeshed interface defined between each one of the manifold pump drive gears and the pump driven gears 324 of a particular one of the rotary, gear-type pump assemblies 310. As is apparent from FIG. 2, while a first arcuate portion of each pump driven gear 324 is drivingly enmeshed with its respective pump drive gear 326, a second arcuate portion of each pump driven gear 324 projects radially outwardly through an end face 402 of the central or intermediate plate 316 of each one of the rotary, gear-type pump assemblies 310 so as to be drivingly enmeshed with a respective one of the manifold pump drive gears. Accordingly, as the drive motor and gearbox assembly, not shown within FIG. 2 but fully disclosed and illustrated within the aforenoted patent to McGuffey, causes rotation of the common drive shaft, and therefore rotation of each one of the manifold pump drive gears, in the counterclockwise direction, the pump driven gear 324 of each one of the rotary, gear-type pump assemblies 310 will be driven in the clockwise direction CW, each one of the pump drive gears 326 will be driven in the counterclockwise direction CCW, and each one of the pump idler gears 328 will be driven in the clockwise direction CW, as viewed in FIG. 2. As can additionally be seen from FIG. 2, the diametrical extent of the cutout region 318 defined within the central or intermediate plate 316 of each one of the rotary, gear-type pump assemblies 310 is substantially larger than the diametrical extent of the pump driven gear 324 of each one of the rotary, gear-type pump assemblies 310.
Therefore, when the liquid, that is, the hot melt adhesive, which is to be pumped through the rotary, gear-type pump assembly 310 and ultimately dispensed from the dispensing assembly, not shown in FIG. 2, is supplied to each one of the aforenoted liquid supply cavities and each one of the liquid accumulator cavities, oppositely oriented liquid flow paths 404,406 are effectively defined between the inner peripheral wall of cutout region 318 and the outer periphery of the pump driven gear 324 despite the fact that the driven gear 324 is being driven in the clockwise direction CW. Subsequently, the liquid portions, originally flowing along the flow paths 404,406, are respectively entrained by means of each pump drive gear 326 and each pump idler gear 328 and conducted toward a common liquid inlet cavity 408 which is effectively formed adjacent to the interface defined between the cutout regions 320,322 that are formed within each central or intermediate plate 316 of each rotary, gear-type pump assembly 310 as may be appreciated from FIG. 2. Ultimately, the hot melt adhesive is, in turn, conducted from the common liquid inlet cavity 408 to control valve assemblies and dispensing nozzles or applicator heads by means of suitable fluid passageways defined within each one of the rotary, gear-type pump assemblies 310 and the drive gear manifold.
While the aforenoted gear pump assemblies of McGuffey were disclosed within the aforenoted U.S. Pat. No. 6,688,498 as being utilized in an integral manner with a hot melt adhesive applicator head or dispensing assembly as a result of, for example, being mounted directly upon the applicator head or dispensing assembly, circumstances may arise when it is not possible or practical to utilize such rotary, gear-type pump assemblies in an integral manner with a hot melt adhesive applicator head or dispensing assembly. One possible instance may be, for example, wherein all of the applicator heads or dispensing nozzles are not disposed at one location. In this instance, the applicator heads or dispensing nozzles are to be fluidically connected to the aforenoted rotary, gear-type pump assemblies by means of suitable hose structures for conveying the hot melt adhesive material from the plurality of rotary, gear-type metering pumps to the applicator heads or dispensing nozzles, however, it is undesirable that such hose structures have substantially large or elongated lengths in that predeterminedly desired pressure levels, and precisely metered or predetermined volumes of the hot melt adhesive material, are difficult to attain and maintain within such hose structures when the hose structures comprise substantial or significant length dimensions. It is therefore desirable to develop a metering station which can effectively be located remotely from a source or supply of the hot melt adhesive material, and wherein further, the hot melt adhesive metering station can then be fluidically connected to the applicator heads or dispensing nozzles by means of relatively short hose structures. In this manner, predeterminedly desired pressure levels, and precisely metered or predetermined volumes of the hot melt adhesive material, can be achieved and maintained such that precisely metered or predetermined volumes of hot melt adhesive material can in fact be dispensed onto predetermined substrate locations.
A need therefore exists in the art for a new and improved remote hot melt adhesive metering station wherein the hot melt adhesive metering station can effectively be located, for example, at a predetermined remote distance from a supply or source of the hot melt adhesive material, that is, an adhesive supply unit (ASU), wherein the remote hot melt adhesive metering station has a compact structure such that a multitude of rotary, gear-type metering pumps can be disposed within a minimal amount of space defined within the remote hot melt adhesive metering station, wherein each one of the rotary, gear-type metering pumps can be independently installed within and removed from the remote hot melt adhesive metering station, and wherein further, the remote metering station can be fluidically connected to the applicator heads or dispensing nozzles by means of relatively short hose structures. In this manner, predeterminedly desired pressure levels, and precisely metered or predetermined volumes of the hot melt adhesive material, can be attained and maintained such that precisely metered or predetermined volumes of hot melt adhesive material can in fact be dispensed onto predetermined substrate locations.